Topic outline
Mapping marine debris from the viewpoint of seabirds and its impact on albatrosses × SDGs
Seabirds feed on small fish and other marine debris as they migrate through the ocean. Black-footed albatrosses, which breed on Torishima Island in the Izu Islands, "encounter" marine debris such as Styrofoam, plastic pieces, and fishing nets. Not only does this increase the risk of ingestion of debris and the birds becoming entangled in fishing nets, but it may also reduce their chances of encountering their natural prey. I would like to contribute to SDG 14 (LIFE BELOW WATER) through research on the impact of marine debris on the marine ecosystem.
Mapping marine debris from the viewpoint of seabirds and its impact on albatrosses
Bungo Nishizawa
National Institute of Polar Research
Research Fellow of Japan Society for the Promotion of Science
A joint research team of the Yamashina Institute for Ornithology, Nagoya University, the University of Tokyo, Tokyo University of Agriculture and Technology, and Hokkaido University, led by Bungo Nishizawa of the National Institute of Polar Research (also a research fellow of JSPS), has conducted a biologging study of the black-footed albatross (Fig. 1) to investigate the distribution of large marine debris and the attraction process of the black-footed Albatross to marine debris.
Black-footed albatrosses which breed on Torishima Island in the Izu Islands migrate over a wide area of the open ocean in search of squids and fishes as food. The research team attached GPS- and video-loggers to 13 black-footed albatrosses and analyzed the acquired data, which revealed that about 70% of the birds (9 out of 13) had "encountered" marine debris such as styrofoam, plastic pieces, and fishing nets. One of the birds was actually filmed pecking at the debris. Furthermore, the distribution of debris was found to be concentrated in the waters with weak currents on the south side of the Kuroshio Current, which is the main foraging area for this species, and this is considered to be a place where there is a particularly high risk of accidental ingestion of debris and sea birds becoming entangled in fishing nets. Furthermore, we found that black-footed albatrosses that landed near debris found it on average about 5 km before, and once they landed near the debris, they stayed there for about 12 minutes. This is about the same amount of time they spend foraging each time, indicating that being attracted to a lot of debris may reduce their chances of encountering their natural prey.The results were published online in the international journal Scientific Reports on May 25, 2021.
Figure 1
Breeding black-footed albatrosses Phoebastria nigripes (left) and a black-footed albatross with a video-logger (black arrow) attached to its abdomen (right). The head is covered with a cloth to attach the logger safely. After the survey, the logger can be removed without damaging the black-footed albatross.
Location: Torishima Island, Izu Islands
Photos: Bungo Nishizawa
Introduction
The amount of marine debris, including plastics, is increasing worldwide, and there are concerns about its impact on marine organisms. For this reason, the distribution of marine debris has long been investigated by visual surveys from ships and airplanes and by collection using plankton nets. However, the distribution of marine debris in the open ocean, far from land, and the overlap with foraging areas of seabirds, which frequently feed on marine debris, have not been well studied.
Among seabirds, albatrosses, which feed on a wide range of food floating on the ocean surface, are known to feed more frequently on marine debris, especially plastics. Recent advances in bio-logging technology have made it possible to attach GPS- and video-loggers to albatrosses to reveal detailed foraging behavior, such as when, where, and what it is eating. In this study, in the process of ecological research using such technology, we investigated the distribution of marine debris from the viewpoint of seabirds, and succeeded in clarifying the degree of the overlap with foraging areas and behavioral responses to debris.
Methods and Results
On Torishima Island in the Izu Islands, about 580 km south of Tokyo, the research team attached GPS-loggers (which record the location at 2-minute intervals) and video-loggers (which record 3-second videos at 2-minute intervals during daylight hours) onto black-footed albatrosses, Phoebastria nigripes, while they ware breeding (Fig. 1). We collected and analyzed location information and 8,492 video data from 13 birds. As a result, a total of 16 pieces of marine debris, including styrofoam and fishing gear floating on the sea surface, were filmed by nine of the birds (Fig. 2). While they sometimes passed over the debris (Fig. 2a), they sometimes landed near it, and one of them was shown actually pecking at a red and white plastic sheet with its beak (Fig. 2f). They were also recorded foraging for natural food (squids and fishes) (Fig. 3).
Figure 2
Examples of marine debris recorded by video-loggers fitted on black-footed albatrosses. Styrofoam (a), plastic with barnacles (b), styrofoam with barnacles (c), fishing net with barnacles (d), entangled rope and fishing net (e), and a black-footed albatross pecking at a plastic sheet (f). (a) and (b)-(f) were recorded during flight and landing, respectively, and were cropped as images. (a) shows the beak and a part of the chest of the individual with the recorder.
Figure 3
Examples of squids (a, b) and fishes (c, d) recorded by video-loggers attached to black-footed albatrosses. (a) shows the beak of the individual with the recorder. The images are cropped from the videos recorded during landing.Next, we defined the locations where the images of marine debris were recorded as the locations where the black-footed albatrosses "encountered" the debris. We identified the locations by comparing the time when the images were recorded with the GPS location information. In the same way, we also identified the foraging areas and analyzed the overlap between them (Fig. 4). As a result, we found that the black-footed albatrosses foraged in several areas around the Izu Islands (purple lines in Fig. 4). The highest number of encounters with debris was recorded in waters with weak currents south of the Kuroshio Current (red circles in Fig. 4). Comparing the locations, the debris encountered was within the foraging areas. Therefore, those areas are considered to have a high potential risk of debris ingestion and entanglement in fishing nets.
Figure 4
Distribution of marine floating debris (red circles) encountered by black-footed albatrosses at sea in relation to their foraging area (purple lines: estimated by locations where the birds fed on squid or fish). GPS tracks of 23 foraging trips made by 13 birds from Torishima (yellow triangle) are shown by gray lines, with green sections symbolizing when concomitant video records were available. Black arrows show surface ocean current during the field survey.Furthermore, to determine when the black-footed albatrosses found the debris, we used data from the 9 times they landed near the debris. The location of the debris was analyzed by considering the time of detection as the time when the migration trajectory changed the most in the 30 minutes before reaching the location of the debris. Previous studies have suggested that albatrosses use their sense of sight and smell (the smell emitted by marine organisms such as barnacles attached to debris) to recognize marine debris. The analysis revealed that the black-footed albatrosses spotted debris an average of 4.9 km in front of them and actively flew toward the debris from there (Fig. 5a). In addition, once they were attracted by the debris and landed, they stayed there for an average of 12 minutes. This is about the same amount of time as they spend foraging for natural food (squids and fishes) (Fig. 5b). Therefore, increased encounters with marine debris may not only increase the risk of ingestion and entanglement but may also limit the amount of time spent foraging for natural prey.
Figure 5
Comparison of the behavioral response of black-footed albatrosses to debris and prey (squids and fishes). Reaction distance toward debris and prey (a). On-water bout durations between those with debris and prey (b).
Future prospects
In this study, we used a bio-logging technique to investigate the distribution of marine debris from the viewpoint of seabirds, and to reveal the overlap with foraging areas and the process of attraction to debris. Black-footed albatrosses did not sit near all the debris they encountered; in some cases, they passed over the debris. In fact, we were not able to evaluate how the degree of attraction differs depending on the type of debris, which is an important issue for future studies. There are 22 species of albatrosses in the world, and many of them are in danger of extinction. It is hoped that the video-loggers and GPS-loggers will be applied to a larger number of albatrosses in the future to identify areas at high risk of encountering marine debris and to better understand the impact on marine life.
Publication
Journal: Scientific Reports
This article is published under a CC BY license (Creative Commons Attribution 4.0 International License).
Title: Mapping marine debris encountered by albatrosses tracked over oceanic waters
Authors:
Bungo Nishizawa (National Institute of Polar Research)
Jean-Baptiste Thiebot (National Institute of Polar Research)
Fumio Sato (Yamashina Institute for Ornithology)
Naoki Tomita (Yamashina Institute for Ornithology)
Ken Yoda (Graduate School of Environmental Studies, Nagoya University)
Rei Yamashita (Atmosphere and Ocean Research Institute, The University of Tokyo)
Hideshige Takada (Laboratory of Organic Geochemistry, Tokyo University of Agriculture and Technology)
Yutaka Watanuki (Graduate School of Fisheries Sciences, Hokkaido University)
URL: https://www.nature.com/articles/s41598-021-90417-x
DOI: 10.1038/s41598-021-90417-x
Published: 25 May 2021
This study was supported by JSPS KAKENHI Grant Numbers A16H0176816 (H.T.) and 19J01267 (B.N.).
